Hello,
> >While doing online defragmentation do we move the blocks corresponding to
> >extent index ? The reason why i am asking this is to understand the
> >usefulness of doing a ext4migrate followed by defrag. I understand that
> >defragmentation in general will improve the performance. But with respect
> >to ext4migrate we are not touching the data blocks. Instead we build the
> >extent map and if that requires to have an extent index block then we
> >allocate one. I am trying to understand what would be the performance
> >impact of this and whether doing a defrag really improve the performance.
>
> I think converting a file to extents has the benefit for the performance of
> block searching. If we want to improve also the performance of reading
> file data, we have to run the defrag after that.
Yes. On the other hand I believe that some people would like to use
defragmentation but stay with ext3. For them conversion to extents is
no-go.
> >Also looking at the version 0.4 I see that defrag ioctl only work if we
> >have EXT4_EXTENTS_FL flag set. What are the plans for making defrag work
> >with indirect block map inode ?
>
> Unfortunately, my defrag doesn't support an indirect block file.
> But we can reduce fragments in the file with the defrag just after
> ext4migrate.
>
> In my opinion, to keep the ioctl simple and small is very important
> for ease of maintenance. So I would rather not support indirect block
> files in the ioctl. Instead, I can add the call of the migration
> ioctl to my defrag tool in order to defragment indirect block files.
> How do you think of it?
Yes that could be useful but I don't think it's a complete solution
for people that don't want to migrate.
Honza
--
Jan Kara <[EMAIL PROTECTED]>
SuSE CR Labs
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